Background & Objectives: Acute optic neuritis in majority of cases, especially young females, is a common presentation of multiple sclerosis. Visual evoked potential (VEP) study is a non-invasive method for evaluation of nerve conduction of optic nerve. This study is an attempt of follow patients with acute optic neuritis and VEP variations over the time.

 Methods: VEP was studied in 30 patients with acute optic neuritis (25 females (83.3%) and 5 males (16.7%) with a mean age of 28.77±9). Clinical examinations and brain MRI study were performed on each. Examinations were repeated 1 and 6 months later. Statistical analyses were performed with SPSS software (rel.11).

 Results: Physical examination revealed another neurologic abnormality in 12 patients (40%). Brain MRI in 19 patients (63.3%) was abnormal. Latency of P100 was abnormal in all cases and only in 7 cases VEP was in normal range after 6 months. Definite MS was diagnosed in 15 cases (50%) and probable MS in 4 patients (13%). P100 amplitude in first study had no prognostic value for recovery.

 Conclusion: VEP has a sensitivity of about 80% for optic nerve injury and the comparison between two eyes is required for the diagnosis of this disorder. Careful clinical examination and brain MRI in the first admission as well as follow-up activities should be done for early detection of multiple sclerosis.